Close to his prime but past it somewhat.
Its more to do with the stylistic demographics of his division. No elite wrestlers with good submission grappling or power for many years at MW.
Chock the division full of even Sonnen types let alone Weidman types rather than the 1D brawlers (Leben, Cote) / 1D BJJ guys (Maia, Lutter, Leites) / jack-of-all-trades but not elite anywhere guys (Marquardt, Okami) he feasted on, his run have would looked a lot different.
Even the LHW's were tailor made to tee-up a showcase (Irvin - to counter program Fedor on Affliction, Forrest - to build back Anderson's mystique after the Leites debacle and Bonnar - another fight to showcase for Brazilian fans)
Most people know Hendo (coming off a loss at both MW and LHW), Vitor (coming off 18 months layoff) Rich x2 and Sonnen (because it was one of the rare times he was stylistically challenged) were Anderson's best wins
Even at 9-0, a green Weidman would have given trouble to Anderson at any point in his career